It is known in 3GPP standard that a User Equipment, UE, may interact with Evolved Packet System, EPS, using the Evolved Universal Terrestrial Radio Access Network, E-UTRAN, radio access. UE related control signaling is handled by Mobility Management Entity, MME, with support of subscription information provided by the Home Subscriber Server, HSS. User payload is handled by the Serving Gateway, S-GW, and the PDN Gateway, PGW. The PGW may interact with a Policy and Charging Rules Function, PCRF.
3GPP Technical Specification TS 23.401, 24.301 and 29.274 elaborate how the UE shall receive it's IP address(es).
It is the PGW that is responsible for allocating and releasing the IP address used by the UE, except in cases where there is a static IP address/prefix stored in the HSS subscription record. In the latter case the PGW uses the IP address/prefix received during the default bearer establishment and delivers it to the UE in the same way as a dynamic IP address.
The UE sets the requested PDN type during an attach or PDN connectivity procedure based on its IP stack configuration, but the PDN type can be modified by the MME based on subscription data received by the HSS and/or operator preferences, and also by the PGW based on operator preferences.
The standard does not allow an operator to restrict the IP address allocated to the UE in all cases. In worst case the UE will end up with double amount of reserved resources in access network, i.e. two default bearers to the same APN, due to lack of operator control and if the standard is followed.
For a general packet radio service, GPRS, system the GPRS support node, GGSN has the same function as the PGW.